In the oil and gas industry in this century the number of inclined horizontal wells have increased and their design, which enhances the productive formation drainage area has become dramatically complex. It is believed that a horizontal well may have a larger contact surface with the rock formation, which increases the recoverability coefficient of hydrocarbons from the well and its intake capacity. Hydrocarbons influx stimulation and construction, development, and maintenance of such wells are substantially different from hydrocarbon production technologies through vertical wells, and thus, the stimulation methods used for vertical wells mostly are not suitable for the horizontal wells.
For example, a horizontal well acidizing allows to penetrate only a few meters deep into the formation, however, most of the interval will remain clogged with mechanical impurities, drilling fluids, or other deposits that occur in the process of drilling, exploration, and exploitation.
The prior art methods describe stimulation of the bottom hole zone of the vertical wells by physical fields by means of creating a depression-repression pressure surges (Russian Patent Nos. RU 2276722 C1 (2006); RU 2310059 C1 (2007); RU 2373386 C1 (2009)). These methods, however, cannot be used in horizontal wells because of the device dimensions, specific design features, and its delivery into a horizontal wellbore.
The prior art methods known for the stimulation of hydrocarbons using various hydraulic fracturing (HF) methods are described in Russian Patent Nos. RU 2278955, Class E 21B 43/16, E 21 B 43/27 (2006) and Patent No 2442886 (2012). However, these proposed methods are very complicated, highly expensive, require significant preliminary preparation of the stimulation and wells, have very stringent requirements for the selection of wells for the hydro-fracturing because of the geological and technical accumulations and wells location in the field, and can be successful if all technical and technological requirements, such as formation thickness, a considerable distance from the oil-water contact (OWC) and gas-oil contact (GOC), significant formation separation, the specific selection of the fracturing and killing fluids, formation anisotropy, and reliable permeability information, are observed which a lot of times are not in the industry or information for building design effects is not sufficient. Quite often hydraulic fracturing (HF) leads to a breakthrough of formation waters and premature water breakthrough.
It is well-known that during drilling of the horizontal wells, porosity and permeability properties of the bottom hole formation are affected by invasion into the drilling fluid formation, invasion into the drilling fluid filtration layer, invasion into the cement filtration layer, perforation destruction and mother rock condensation, mechanical impurities in the completion or killing fluids penetrating into the formation or clogging perforation, invasion of the completion or killing fluids into the formation, formation clogging with natural clays, paraffin and asphaltene deposits in the formation or perforation, saline deposits in the formation or perforation, formation emulsification, and injection of solvent with mechanical impurities.
All of the above leads to a decrease in bottom hole permeability, and hence, productivity, often more than 60% of the design, and in worst cases, if damage is very deep, to the complete cessation of well production.